Sieve bed for a sifting machine

ABSTRACT

The invention pertains to a sieve bed for a sifting machine, consisting of rectangular sieve elements ( 10 ), which are attached to a support frame ( 1 ) with their edges abutting each other, the support frame being provided with mushroom-shaped mounting pins ( 3 ), each of which is provided with a head which engages in an interlocking manner in corresponding recesses ( 11   a  and  11   b ) of the sieve elements ( 10 ).  
     To facilitate the assembly and disassembly of the sieve elements in a sieve bed of this type and to protect the connection from premature wear the invention proposes that the receptacle ( 11 ) for the head ( 4 ) of the mounting pin ( 3 ) be closed off at the top; that the receptacle ( 11 ) for the head ( 4 ) of the mounting pin ( 3 ) be provided at the bottom with an entrance opening for the head ( 4 ) of the mounting pin ( 3 ); and that the wall of the receptacle ( 11 ) be provided with an inward-projecting bead ( 12 ), which can be snapped under the head ( 4 ) of the mounting pin ( 3 ).

CROSS REFERENCES

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/936,718 filed on Feb. 13, 2002, which is itself based uponPCT patent application no. WO 00/064599 A3 filed on Apr. 26, 2000 thatwas itself based upon German patent application no. 199 18 824.6 whichwas filed on Apr. 26, 1999.

BACKGROUND OF THE INVENTION

[0002] The invention pertains to an improved sieve bed for a siftingmachine. More particularly, the invention relates to an improvedmounting pin that allows for a maximum useful surface area for the sievebed and which also securely mounts a plurality of sieve elements on asupport frame of the sieve bed.

BRIEF DESCRIPTION OF THE RELATED ART

[0003] Various structures for screening or sifting particulate materialsare known in the art. In general, a screening or sifting machineconsists of a plurality of sieve elements (also referred to as screeningpanels and screen modules, among others) that are attached to a supportframe with their edges abutting one another to create a contiguoussifting surface. Existing sifting machines can be loosely divided intothose devices having sieve elements that are secured to an underlyingsupport frame by means of projections which extend downwardly from thesieve elements themselves, and those devices which are secured to anunderlying support frame by means of projections which extend upwardlyfrom the support frame to mate with complimentary cavities formed in thesieve elements.

[0004] It is known that the mounting pins can be designed as integralparts of the sieve elements. In one case, half pins are molded onto theopposing edges of adjacent sieve elements; these half-pins are designedto work together to form a whole pin. The half-pins can be driven orsnapped jointly into a mounting hole in the support frame. A sieveelement such as this suffers from the disadvantage that the mountingpins must necessarily consist of the same material as the sieveelements; this can detract from the quality of the attachment if thesieve elements consist of a relatively soft material. In addition, it isalso more difficult in particular to remove the sieve elements, because,each time the elements are removed, the relatively long half-pins mustbe pulled out of their mounting holes. Another disadvantage of the sievebed of this type consists in that, after the sieve elements have becomeworn out, the mounting pins also must be replaced along with the sieveelements. They cannot therefore simply remain on the support frame.

[0005] A specific example of the former type of sieve bed is disclosedin U.S. Pat. No. 5,938,042 to Freissle et al. The Freissle patentdiscloses a support frame made of up of a plurality of frame componentsin which a pair of complimentary elongate members, each having aplurality of cavity defining formations, are secured to one another soas to form a unitary frame component having a plurality of cavities forreceiving respective socket elements therein. When arranged side by sideupon a sub-frame comprising a plurality of support beams, the framecomponents form a support frame to which a plurality of screening panelsmay be secured. Protrusions depending from the under surface of thescreening panels are inserted into socket elements retained within thecavities of the respective frame components. Some of the disadvantagesof this design include the fact that the frame components comprise toomany constituent parts, require numerous and expensive manufacturingsteps, require a higher degree of maintenance, and exert a hold downforce upon the screening elements that is limited by the strength of theelastic material from which the protrusions depending from theundersurface of the screening panels are made.

[0006] A sieve bed of the latter type described above is known from, forexample, DE-GM 78-11,183. In this known sieve bed, the mounting pins aredriven from above into the receptacles formed by two adjacent sieveelements. The pins are thus able to pass into appropriately locatedmounting holes in the support frame and are then spread and tensioned byan expanding mandrel, which can be driven into the mounting pin.

[0007] This design of a sieve bed suffers from several disadvantages. Afirst significant disadvantage is that the receptacle for the mountingpin must be open at the top; this means that it is exposed to thewearing action of the highly abrasive material being sifted. Inaddition, there is the danger that fines from the material being siftedcan get into the attachment area, where they can interfere with theremoval of the sieve bed. Finally, both the installation and removal ofthe previously known sieve bed are relatively cumbersome because themounting pins must be completely removed and then reinstalled each timethe sieve elements are replaced.

[0008] Another example of the latter type of sifting machine isdisclosed in U.S. Pat. No. 5,049,262 issued to Galton et al. The Galtondevice consists of a deck frame made up of a series of rigid elongatemembers spaced apart in parallel relationship and interconnected atregular intervals by cross members. The elongate frame members eachinclude a series of mounting apertures that are spaced apart along eachmember and oriented normal to the plane of the elongate member forpositioning and removably connecting screening modules to the frame.Lock pins are inserted into the mounting apertures so that a top portionof the lock pin extends upwardly from the elongate frame members.Recesses in the edges of the respective screening modules receive theupper portion of these lock pins therein for the purpose of securing thescreen modules to the frame. The recesses in at least one embodiment ofthe screening modules of the Galton patent are constructed and arrangedso that the upper portion of the lock pins are wholly encompassed withinand between respective screening modules placed over a lock pin. In thisembodiment, no portion of the lock pin extends to or above the uppersurface of the screening modules.

[0009] Some of the disadvantages that this design suffers from includethe fact that given that the lock pins described in the Galton patentmust be received within an aperture formed through a substantiallyhorizontal surface of the elongate frame members, the frame members areconstrained to be at least as wide the widest portion of the lock pinsthemselves. The relatively large surface area of the elongate framemembers reduces the useful area of the screening modules in theassembled sifting machine and thereby decreases the magnitude of thematerial throughput of the sifting machine. What is more, because thelock pins of the Galton patent must be made from an elastic material inorder to insert the lock pins into the mounting apertures in theelongate frame members, the hold down force that the lock pins may exertupon the screening modules is necessarily limited, thereby increasingthe likelihood that the screening modules will become dislodged underheavy loading conditions.

[0010] In general, wherein elastic protrusions, projections, or lockpins are utilized to secure a sieve element, screening panel, orscreening module to a support frame of a sifting machine, the hold downforce that may be asserted in these screening elements is necessarilylimited. And, as the screening elements themselves are relativelyelastic, impact forces imparted thereto by materials being dropped orotherwise placed on the sifting machine are transmitted directly to themechanisms which secure the screening panels to the support frame of thesifting machine. These impact forces can readily dislodge screeningelements not securely attached to the support frame, thereby requiring auser to suspend operation of the sieve machine while the screen panel isreplaced. Where a screen panel becomes dislodged during operation, theparticulate matter being sifted may also cause undue wear on the screenpanels and on the support frame.

[0011] In order to reduce the likelihood of a panel becoming dislodgedduring operation, relatively thin and elastic screening panels have beenused. While these thinner screening panels would be subject torelatively higher deflections, their elastic nature would reduce themagnitude of the forces imparted to the mechanisms used to secure thepanels to the sub-frame. The use of relatively thin screening panels hasin turn resulted in shorter useful lives for the screening elementsthemselves because the abrasive nature of the materials being screenedor sifted tends to wear out the relatively thinner panels at anunacceptably fast rate.

[0012] Prior art sifting machines also often fail to maximize the usefularea of the screening elements or modules. The term “useful area” isused herein to indicate the total area of the screening surface that maypass therethrough particulate material that is being sifted. Generallyspeaking, a larger useful area equates with a larger total throughput ofparticulate materials. This in turn results in higher efficiencies and agreater return on a user's investment. Unfortunately, prior art devicesthat make an effort to maximize the useful area of the screening surfacetend to become rather complicated and comprise a great many parts thatmay be susceptible to undue wear and tear themselves.

OBJECTIVES OF THE INVENTION

[0013] Accordingly, it is an objective of the present invention toprovide a retaining mechanism for retaining a plurality of sieveelements on a support frame that maximizes the useful area of a sievebed and provides a strong point of attachment for the sieve elements.The present invention also provides for a substantially rigid retainingmechanism that is resistant to wear and easily installed and replaced ifnecessary. Another objective of the present invention is to provide aretaining mechanism that increases the strength of the connectionbetween the sub-frame of the sieve bed and the sieve elements and thatpermits the relative strength and thickness of a sieve element to beincreased above what is normally considered useful in the prior art. Itis a final objective of the present invention to provide a sieve elementthat will prevent fines and other particulate material from gainingaccess to the retaining mechanism used to secure the sieve elements to asupport frame.

[0014] These and other objectives and advantages of the invention willappear more fully from the following description, made in conjunctionwith the accompanying drawings wherein like reference characters referto the same or similar parts throughout the several views.

SUMMARY OF THE INVENTION

[0015] In the sieve bed according to the invention, the receptacle forthe head of the mounting pin is closed off at the top, so that the headof the mounting pin cannot be worn down. Instead, the head is in aprotected state underneath the top surface of the sieve elements, theedges of which are arranged in abutting fashion. Because the receptaclefor the mounting pin has an opening at the bottom for the head of themounting pin, the sieve elements, which consist of elastic material, canbe easily pressed down from above onto the heads. Thus the bead on thewall of the receptacle will snap into the space underneath the head ofthe mounting pin and thus fix the sieve element in place on the mountingpin and the support frame.

[0016] Because of the way in which the sieve elements and mounting pinsare designed, as explained above, it is possible to fix the sieveelements in place by pressing down on them from above and then by simplyhitting them with a hammer above the mounting pins. For removal, asuitable tool is inserted into the joint between two adjacent sieveelements, and then the sieve element is pried off the heads of themounting pins under elastic deformation of the edge of the element. Theinstallation and removal of the sieve elements is therefore as simple ascould be imagined; even better, the mounting pins can remain on theframe which is an especially advantageous feature

[0017] To facilitate the insertion and snap-in engagement of themounting pin in its mounting hole, it is also provided that the top edgeof the head of the mounting pin is rounded or beveled,

[0018] An advantageous embodiment of the sieve bed according to theinvention provides that the mounting pins are made of a plastic withelastic properties and that the pins can be inserted into and held inplace in the mounting holes of the support frame. These mounting pins ofelastic plastic can themselves be easily attached to the support frameand removed from it again if it is ever necessary to replace one ofthem.

[0019] When mounting pins of plastic are used, it is advisable toprovide a support shoulder a certain distance below the head of themounting pin, this shoulder resting from above on the edge of themounting hole in the support frame. This support shoulder ensures that amounting pin which has been snapped into the mounting hole in thesupport frame is always at the correct height with respect to thesupport frame.

[0020] To fix the mounting pin of plastic in place in the support frame,it is advisable for each mounting pin to have a bulge a certain distanceunderneath the support shoulder, the diameter of this bulge area beinggreater than the diameter of the mounting hole in the support frame.This bulge can thus be snapped into the space under the edge of themounting hole this prevents the mounting pin from coming loose from thesupport frame during the installation of the sieve elements

[0021] To avoid excessive forcing or damage to the outer contour of themounting pin, the plastic-mounting pin is advisably provided with aslot, which extends up from the bottom all the way into the area of thebulge. As a result, the pin can be compressed in the radial direction

[0022] To facilitate the installation of the plastic mounting pins, eachmounting pin has an annular collar between its bulge and the bottom end,the diameter of this collar being slightly greater than the diameter ofthe mounting hole in the support frame. Thanks to this annular collar,the plastic mounting pin can be inserted by hand and temporarily held inplace in the mounting hole of the support frame. This is done bycompressing the slotted area of the mounting pin radially by hand and byintroducing the pin into the mounting in this compressed state. Thusheld in place temporarily, the mounting pin stays in position until itis driven into the mounting hole by the effective use of a hammer andthus snapped into its fastening position behind the bulge.

[0023] Finally, the bottom end of the plastic mounting pin is rounded orbeveled to make it easier for the pin to be installed.

[0024] The plastic mounting pins can also be attached to the supportframe in a different way. For example, it is possible for the mountingpin to have an axially running longitudinal hole extending through itinto which an expanding mandrel can be driven to fix the mounting pin inthe mounting hole of the support frame. When this method of attachmentis used, the outer contour of the mounting pin in the area underneaththe support shoulder can be that of a simple cylinder.

[0025] In another embodiment of the sieve bed according to theinvention, the mounting pins consist of steel and are welded to thesupport frame. In this case, the mounting pins are advisably providedwith a slot at the bottom, by means of which they can be mounted onvertical webs of the support frame before being welded to it. Theseslots make it extremely easy for the mounting pins to be welded in thecorrect position to the support frame. The use of vertical webs on thesupport frame is an extremely advantageous way of increasing the activesieve area around the edges of the sieve elements. This is because thevertical webs of the support frame are much narrower than the frameparts with the mounting holes provided in accordance with the precedingdesign.

[0026] One embodiment of a support frame for a sieve bed comprises aplurality of elongate ribs each having a thickness that is substantiallysmaller than its height. These thin ribs are arranged side-by-side upona sub-frame such that the upper edges of the ribs are substantiallyco-planar. Each rib has a plurality of substantially rigid mounting pinssecured to its upper edge for securing an array of sieve elements to thesupport frame in abutting juxtaposition. The mounting pins are typicallyspaced along the upper edge of the ribs at between 5 and 14 inches oncenter.

[0027] The mounting pins of this embodiment have a frustoconical uppersurface that, when received within a receptacle formed by a pair ofcooperative apertures formed in adjacent edges of abutting sieveelements, secure the sieve elements to the support frame. The mountingpins may be fabricated from a ferrous alloy, and if so, may be securedto the ribs by welding. Where the mounting pin is welded to the rib, itis preferred to only weld the distal end of the stem of the mounting pinto the rib.

[0028] The heads of the mounting pins are mushroom shaped and have anupper surface that is preferably frustoconical and an under surface thatis preferably substantially flat. A stem is secured to and extends awayfrom the under surface of the head in a substantially perpendicularrelationship to the head. The stem has a slot formed in its distal endthat extends toward the head. This slot is constructed and arranged toreceive therein the upper edge of the rib on which it is mounted andaids in locating the mounting pin on the rib. To this end, it ispreferred that the slot formed in the stem of the mounting pin terminatein a substantially flat shoulder that is in a planar perpendicularorientation with respect to the axis of symmetry of the stem of themounting pin.

[0029] The upper surface of the head of the mounting pin is preferablyangled outward and downward at approximately a 45° angle from a planeperpendicular to an axis of symmetry of the head of the mounting pin.And while the undersurface of the head is preferably perpendicular tothe stem, the undersurface may angle away from this orientation bybetween +50° and −5°.

[0030] Another embodiment of the mounting pin is stamped from a metalplate and comprises a hollow cylindrical body with an upper end and alower end. The lower end of the body has an aperture formed therethroughand the upper end of the body has depending downwardly therefrom asubstantially frustoconical surface. This type of mounting pin may besecured to the upper edge of a rib by welding the mounting pin to therib through the aperture formed in the cylindrical body of the pin.

[0031] This embodiment has a cylindrical body with a bore formedentirely therethrough. The body has a mushroom shaped head with afrustoconical upper surface that extends from an upper edge thereof. Thebore that is formed through the body has an outlet at a lower endthereof that is constructed and arranged such that the upper edge of asupporting rib may be accessed therethrough for the purpose of securingthe mounting pin on the rib. As is described above, welding is onemethod where by the mounting pin may be secured to a supporting rib.

[0032] A sifting machine that includes a mounting pin such as that justdescribed is made up of a subframe and a support frame that rests on andis secured to the subframe. The support frame has a plurality ofelongate thin ribs with upper edges that are arranged in a substantiallycoplanar relationship. Each of the ribs is further provided with aplurality of mounting pins. The mounting pins each have a cylindricalbody with a bore formed entirely therethrough. The bodies of themounting pins have a mushroom shaped head with a frustoconical uppersurface that extends from an upper edge thereof. The bore formed throughthe body has an outlet at a lower end thereof that is constructed andarranged such that the upper edge of a supporting rib may be accessedtherethrough for the purpose of securing the mounting pin on the rib.The mounting pin is then secured to the upper edge of the rib by forminga weld between the lower end of the body and the supporting rib throughthe outlet of the bore. The support frame is topped with an array ofsieve elements that is arranged in abutting juxtaposition thereon. Thesieve elements are secured to the support frame by the mounting pinssuch that the head of each mounting pin engages a pair of adjacentrecesses formed in the respective edges of abutting sieve elements. Thepair of adjacent recesses work together to form a receptaclecomplementary to the shape of the head of the mounting pin.

[0033] In order to prevent particulate material from passing between thesieve elements, the sieve elements may be provided with a bead that isformed along the lateral edges of the sieve elements. The beads arelocated such that when the sieve element is placed in abuttingjuxtaposition with one or more additional sieve elements, the beads onthe abutting edges of the respective sieve elements contact one anotherto form a seal therebetween. This seal prevents particulate materialsfrom passing between the sieve elements where they might abrade themounting pins.

DESCRIPTION OF THE DRAWINGS

[0034]FIG. 1 shows a vertical cross section through a sieve bedaccording to the invention in the area of a mounting pin;

[0035]FIG. 2 shows a side view of a mounting pin of plastic;

[0036]FIGS. 3 and 4 show a plan view and a cross section, respectively,of a sieve element of plastic;

[0037]FIGS. 5 and 6 show a plan view and a cross section, respectively,of a support frame with inserted mounting pins of plastic;

[0038]FIG. 7 shows a side view of a mounting pin of steel;

[0039]FIGS. 8 and 9 show a support frame with welded-on mounting pins ofsteel;

[0040]FIG. 10 shows a mounting pin and the method used to fix it inplace on the support frame in accordance with a modified design; and,

[0041]FIG. 11 shows a mounting pin seated upon a vertical rib member ofa support frame;

[0042]FIG. 12 shows the mounting pin of FIG. 11 and the method wherebythis mounting pin secures a pair of sieve elements to a support frame;

[0043]FIG. 13 an embodiment of a mounting pin formed by stamping securedto the upper surface of a vertical rib of a support frame; and,

[0044]FIG. 14 shows the mounting pin of FIG. 13 and the method wherebythis mounting pin secures a pair of sieve elements to a support frame.

DETAILED DESCRIPTION

[0045] Although the disclosure hereof is detailed and exact to enablethose skilled in the art to practice the invention, the physicalembodiments herein disclosed merely exemplify the invention, which maybe embodied in other specific structure. While a preferred embodimenthas been described, the details may be changed without departing fromthe invention, which is defined by the claims.

[0046]FIG. 1 shows only a part of the support frame, which is identifiedoverall by reference number 1 The support frame 1 has a plurality ofmounting holes 2, only one of which can be seen in FIG. 1. A mountingpin 3, fabricated out of an elastic plastic such as polyurethane isinserted into each of these mounting holes 2 and press-fit tightly inplace. Mounting pin 3 is provided at the top with a head 4, the outsideedge of which is rounded or beveled at the top

[0047] Underneath the head 4, the mounting pin 3 is provided with acircumferential groove 5. Underneath the groove 5 there is a ring-shapedsupport shoulder 6, the diameter of which is considerably greater thanthe diameter of the mounting hole 2 in the support frame 1 and whichrests from above on the edge of this mounting hole 2

[0048] Underneath the support shoulder 6, the diameter of the mountingpin 3 is slightly larger than that of the mounting hole 2, so that atthis point a' tight press-fit of the elastically deformable mounting pin3 in the mounting hole 2 is achieved.

[0049] The mounting pin 3, furthermore, is provided with a bulge 7 acertain' distance below the support shoulder 6. This bulge tapers in theupward direction toward support shoulder 6 at a shallow angle and in thedownward direction at a steep angle. The diameter of this bulge 7 issignificantly greater than the diameter of the mounting hole 2 in thesupport frame 1.

[0050] An annular collar 8, the diameter of which is greater than thediameter, of the mounting hole 2 in the support frame 1, is providedbetween the bulge 7 and the bottom end of the mounting pin 3. The outercircumference of the bottom end of the mounting pin 3 is rounded orbeveled just like the head 4. Finally, the lower section of the mountingpin 3 is provided with a vertical slot 9, which extends up from thebottom, ending slightly beyond the area of, the bulge 7.

[0051] The effect of slot 9 is to allow the lower section of themounting pin 3 to be easily squeezed radially by hand upon insertioninto the mounting hole 2 of the support frame 1, so that the annularcollar 8 can be passed through the mounting hole 2. The mounting pin 3is thus temporarily held in place in the, mounting hole 2, then a strongblow from above with a hammer can drive the mounting pin 3 all the wayinto the mounting hole 2. As part of this process, the bulge 7, incooperation with the slot 9, allows the mounting pin 3 to snap into themounting hole of the support frame 1.

[0052] The head 4 of the mounting pin 3 serves to hold the two abuttingsieve' elements 10 a and 10 b in place. For this purpose, these sieveelements 10 are provided on their abutting edges with correspondingrecesses 11 a and 11 b, which work together to form a receptacle 11,which corresponds to the shape of the head 4 of the mounting pin 3, andin which the head 4 of the mounting pin, 3 engages in an interlockingmanner. This receptacle 11 is closed off at the top, whereas it has anentrance opening in its bottom for the head 4 of the mounting pin 3, thediameter of this opening being smaller than that of the head 4. Thisentrance opening is formed by a circumferential bead 12, which consistsof the two bead sections 12 a and 12 b projecting inward from the wall,of the receptacle 11. The bead snaps into the groove 5 in the mountingpin 3 under the head 4.

[0053] The sieve elements are assembled by laying them with their edgesabutting each other on the support frame 1 in such a way that therecesses 11 a and 11 b, come to lie above the heads of the previouslyinstalled mounting pins 3. Then the sieve elements 10 are fixed in placeby hitting them with a hammer above the heads 4 of the mounting pins 3.As a result, the elastic material of which the heads 4 of the mountingpins 3 are made is elastically deformed; this allows the heads to enterthe receptacles 11, where they snap in place, behind the bead 12

[0054] For disassembly, a suitable tool is inserted into the jointbetween two, abutting sieve elements 10. With the help of this tool, thesieve elements 10 are then pried off the mounting heads 4 of themounting pins 3 under elastic deformation of their material.

[0055] Both assembly and disassembly are therefore as simple as could beimagined and can be accomplished with very simple tools.

[0056]FIG. 2 shows a mounting pin 3 by itself with all of its parts as,described above.

[0057] As can be derived from FIGS. 3 and 4, the sieve elements 10 aredesigned as rectangular plates, which are provided over their flatexpanses with a plurality of sieve openings. Along their longitudinaledges, they are provided with the above-explained recesses 11 a and 11b, which work together with the corresponding recesses 11 a and 11 b ofadjacent sieve elements to form the receptacles 11.

[0058]FIGS. 5 and 6 show a plan view and a cross section, respectively,of the support frame 1 with the mounting pins 2 attached to it in themanner described above.

[0059]FIG. 7 shows an alternative embodiment of the mounting pin, whichis made of steel; this pin is identified by the reference number 13. Themounting pin 13 also has a head 14, a groove 15 underneath the head, anda support shoulder 16 underneath the groove To this extent, mounting pin13 is the same as mounting pin 3 described above. Underneath the supportshoulder 16, however, mounting pin 13 is designed as a cylinder 18 witha slot 17 over its entire length. This cylinder can be welded to thesupport frame 2.

[0060] The way in which the mounting pins 13 can be welded to thesupport frame 1 is illustrated in FIGS. 8 and 9. That is, the slot inthe cylindrical section 18 of the mounting pin 13 is placed from aboveonto vertical web 19 of the support frame 1 and fixed in place there bywelds 20.

[0061] In the exemplary embodiment according to FIG. 10, the mountingpin is identified by reference number 23. This mounting pin 23 alsoconsists of an elastic plastic and has a head 24, a groove 25 underneaththe head, and a support shoulder 26. To this extent, mounting pin 23 isthe same as mounting pins 3 and 13 described above.

[0062] The mounting pin 23, however, is designed as a cylinderunderneath the support shoulder 26, and has a longitudinal hole 27extending all the way through it; this hole tapers slightly underneaththe support shoulder 26. An expanding mandrel 28 can be driven fromabove into this tapered longitudinal hole 27; the mandrel thus spreadsthe mounting pin 23 apart underneath the support shoulder 26 in such away that it is held by tension in the mounting hole of the support frame1. If desired, the mounting pin 23 can also be provided with a slotunderneath the support shoulder 26 to make it easier for the pin toexpand.

[0063] An alternate embodiment of the mounting pin 13 of FIG. 7 isillustrated in FIG. 11. The mounting pin of this alternative embodimentis identified by the reference numeral 30. Mounting pin 30 comprises ahead 31 that is secured to a stem 32 having a slot 33 formed in itsdistal end.

[0064] The head 31 of the mounting pin 30 has a frustoconical uppersurface 31A, which forms an angle between 45° and 60° from the axis ofsymmetry 31E of the head 31. Preferably the top 31D of the head 31 isflat but may also be hemispherical or may be omitted, resulting in aconical upper surface 31A. The undersurface 31B of head 31 is preferablyflat, i.e. perpendicular to the axis of symmetry 31E but may also befrustoconical in shape, angling away from perpendicular to the axis ofsymmetry 31E by approximately 5° in either direction. While the surfaces31A and 31B of head 31 may be formed immediately adjacent one another,thereby forming a relatively sharp edge, it is preferred to interpose acylindrical section 31C between surfaces 31A and 31B. Section 31C may beflat, i.e. cylindrical, or it may be radiused to form a gentletransition between head surfaces 31A and 31B. The configuration of thehead 31 of mounting pin 30 is advantageous in that the amount of forcenecessary to insert the head 31 of the mounting pin 30 into thereceptacle 41 formed between the sieve elements 40 is relatively lowwhereas the amount of force required remove the sieve elements 40 fromthe support frame 1 is substantially higher and results in a strongerbond between the support frame 1 and the sieve element 40. This strongerbond in turn reduces the likelihood that a sieve element 40 willunnecessarily become dislodged from the support frame 1.

[0065] The mounting pin 30 is preferably fashioned of steel or anotheralloy that can easily be secured, as by welding, to the vertical ribs 19that form the support frame 1 of this embodiment. However, it iscontemplated that other materials may be used in fashioning the head 31of the mounting pin 30 so long as the head 31 remains substantiallyrigid. By way of example, the head 31 of the mounting pin 30 may becoated or clad with a layer of a ceramic material, a plastic materialsuch as Teflon™, or even plated. Alternatively, the head 31 may befashioned completely from a ceramic material and secured to the stem 32.Preferably, the head 31 will be case hardened, as by carburizing, toincrease the strength and abrasion resisting capabilities of the head31.

[0066] The stem 32 extends away from the head 31, preferably in a normalrelationship to the head 31. The stem 31 is narrower in cross-sectionthan the head 31 and has a slot 33 formed in the distal end of the stem32 opposite the head 31 of the mounting pin 30. The slot 33 extends fromthe distal end of the stem 32 along the stem 32 in the direction of thehead 31, thereby forming a pair of legs 33 b. The slot 33 terminates ina shoulder 33 a that is preferably formed in a perpendicular planarrelationship with the axis of symmetry 31C of the mounting pin 30. Theslot 33 is sized to receive therein the upper edge of a vertical rib 19,with the legs of the stem 32 extending down each side of the rib 19. Theflat shoulder 33 a acts to properly orient the head 31 of the mountingpin above the upper edge of the vertical rib 19. The mounting pin 30 issecured to the rib 19 by welding only the distal ends of the legs 33 bto the respective sides of the rib 19, though the welds could extend upthe legs 33 b if need be. The stem 32 and slot 33 are to be sufficientlylong that the weld 36 will be spaced apart from the upper edge of thevertical rib 19 to an extent that will prevent the welds from deformingthe upper edge of the rib 19 or damaging the hardened head 31 of themounting pin 30. Sizing the stem 32 and slot 33 relatively long alsoadvantageously allows a damaged mounting pin 30 to be cut or ground offof the rib 19 and replaced without damaging or deforming the uppersurface of the rib 19.

[0067] It is preferable to form the mounting pin 30 as a unitarystructure of a suitable steel. This allows the mounting pin 30 to bewelded to a support frame, or alternatively, to be bolted or otherwiseconnected to the support frame. As indicated above, it is alsocontemplated that the head 31 and stem 32 may be fabricated fromdifferent materials. For example, the stem may be fabricated from steelwhereas the head 31 is a ceramic material joined to the stem 32 by anadhesive or by a mechanical fastener. Alternatively, the head 31 may beof steel and the stem 32 may be fashioned from a material such as aceramic.

[0068] Referring again to FIG. 11, it can be seen that the vertical ribs19 have a width that is thinner than the maximum width of the mountingpins 30. The relatively thin vertical ribs 19 maximize the throughput ofthe sieve bed by reducing the resistance to flow, i.e., the ribs 19 donot block the flow of particulate materials through the sieve elements40 of the sieve bed. The ribs 19 are typically arranged in a side byside arrangement over a sub-frame to form the support frame 1 to whichthe sieve elements 40 are secured. Though the ribs 19 are thin, theirdepth may be varied to increase or decrease the maximum load capacitiesof the sifting machine. The vertical ribs 19 are preferably installed sothat their upper edges are coplanar with each other. This ensures thatthe upper surface of the sieve elements 40 will be substantially flat.In addition, the top edges of the vertical ribs are preferably flat andperpendicular to the sides of the rib 19 to properly position themounting pins 30 thereon.

[0069] The vertical ribs 19 are preferably welded to the sub-frame toform the support frame 1, but may also be bolted, screwed, or otherwisesecured to the sub-frame of the sieve bed. The mounting pins 30 aresecured to the upper edge of the vertical ribs 19 at between 5″ and 14″on center. In practice, the vertical ribs 19 may be installed on asub-frame to form the support frame 1 before the mounting pins 30 aresecured to the ribs 19. However, it is preferred to secure the mountingpins 30 to the vertical ribs 19 before the vertical ribs 19 areinstalled on the sub-frame to form the support frame 1. If one or moreof the mounting pins 30 should become worn or damaged, these mountingpins 30 may be individually cut off and replaced, or the entire sectionof vertical rib 19 having the damaged mounting pins 30 thereon may beremoved and replaced with another section of vertical rib 19 andmounting pins 30. The vertical rib 19 with the damaged mounting pins 30may then be repaired at leisure without incurring large amounts ofdowntime for the sifting operation.

[0070]FIG. 13 illustrates adjacent and abutting sieve elements 40A and40B held in place over the support frame 1 by a mounting pin 30 that issecured to a vertical rib 19 of support frame 1. The sieve elements 40Aand 40B are provided on their abutting edges with corresponding recesses41A and 41B which work together to form a receptacle 41 having a shapethat is complimentary to the shape of the head 31 of the mounting pin30. As can be readily understood, the head 31 of the mounting pin 30 isreceived in the receptacle 41 formed between the sieve elements 40A and40B in an interlocking manner. The height of the receptacle 41 is to beno greater than the height of the head 31 of the mounting pin 30.Matching the heights of the receptacle 41 to the height of the head 31of the mounting pin 30 results in a tight engagement between thereceptacle 41 and the head of the mounting pin 30. Preferably, theheight of the receptacle 41 will be slightly smaller than that of thehead 31 so as to create what can be described as a press-fit between thehead of the mounting pin 30 and the receptacle 41.

[0071] Like the receptacle 11 illustrated in FIG. 1, receptacle 41 isclosed off at its top and has an entrance or opening at its bottom sothat the head 31 of the mounting pin 30 may be inserted into thereceptacle 41. It should be noted that the diameter of the opening ofthe receptacle 41 is smaller than that of the head 31. This smalleropening is formed by a circumferential bead 42 that consists of two beadsections 42 a and 42 b that project inwardly from the wall of thereceptacle 41. The bead 42 of the receptacle 41 closely engages theundersurface 31B of the head 31 to hold the sieve elements 40A and 40Bin place upon the support frame 1. In inserting the head 31 of themounting pin 30 into the receptacle 40, the frustoconical upper surface31A of the mounting pin 30 will deflect the bead 42, thereby allowingthe head 31 of the pin 30 to enter. Increasing the angle of the uppersurface 31A eases the entry of the head 31 into the receptacle 42 andconversely, flattening the angle of surface 31A tends to make theinsertion more difficult. Similarly, angling the undersurface 31B of thehead 31 upward will present a frustoconical surface to the entrance ofthe receptacle 41 and will ease the egress of the head 31 from thereceptacle 41. However, it is preferred to form the undersurface 31Bperpendicular to the axis of symmetry 31E of the mounting pin 30 so asto increase the magnitude of the force required to remove the head 31 ofthe mounting pin from the receptacle 41. In addition, it may bedesirable to form cylindrical section 31C so that it runs parallel tothe axis of symmetry 31E. The resulting relatively sharp edge betweenthe undersurface 31B of the head 31 and section 31C would also increasethe magnitude of force required to remove the sieve elements 41 from themounting pins 30.

[0072] The sieve elements 40A and 40B are assembled by laying them withtheir respective edges abutting each other above the support frame 1 insuch way that the recesses 41A and 41B come to lie above the heads 31 ofthe previously installed mounting pins 30. The sieve elements 40A and40B are then fixed in place by forcing them down on to the mounting pins30 as by striking them with a hammer. As a result, the material of whichthe sieve elements 40A and 40B are made to elastically deform to allowthe heads 31 of the mounting pins 30 to enter the receptacles 41 whichsnap in place below the beveled undersurface 31B of the mounting pins30. For disassembly, a suitable tool is inserted into the joint betweenthe two abutting sieve elements 40A, 40B, and with the help of thistool, the sieve elements 40A, 40B are then pried off the mounting heads31 of the pins 30 under the elastic deformation of the material of thesieve elements 40A, 40B.

[0073] Because the diameters of the mounting pins 30 are relativelysmall, very little useful area is lost. The only useful area that islost is due to the lands 44 that define the upper surface of the portionof the sieve element 40 where the receptacle 41 is located in the sieveelement. See FIG. 3. Specifically, the diameter of the receptacle half41 a or 41 b expressed on the upper surface of the sieve element 40 aslands 44 are at most twice the diameter of the head 31 of the mountingpin 30 received within the receptacle 41. The small amount of lostsurface area 44 results in the maximum amount of useful area for thesifting machine and hence, the maximum throughput for particulatematerials. Another benefit to the small amount of lost surface area isthat it is possible to utilize more mounting pins 30 in a givenapplication, without needlessly sacrificing useful area. In a rigoroussetting more mounting pins 30 may be used to secure the sieve elements40 to the support frame 1, thereby decreasing the likelihood that asieve element 40 may become dislodged during use. Conversely, because ofthe high forces necessary to dislodge the sieve elements 40 from themounting pins 30, and because the mounting pins 30 incur very littlelost surface area, a sifting machine may be designed that maximizes boththroughput of particulate materials and the weight capacity of thesifting machine without having to sacrifice the former for the latter.

[0074] To increase the useful life of the sieve elements 40 and mountingpins 30, it is also desirable to form a seal or lip 46 around theperiphery of each sieve element 40 as illustrated in FIG. 13. Therespective seals 46 on abutting sieve elements 40 form a barrier toparticulate materials and fines that might otherwise insinuatethemselves into the joint between the respective panels or into thereceptacles 41 in which the heads 31 of the mounting pins 30 arereceived. When particulates or fines fill the joints between the panelsor infiltrate the receptacles 41, the mounting pins' ability to securethe sieve panels 40 to the support frame 1 may be compromised, therebyresulting in the inadvertent dislodgement of a sieve panel. While thiscannot, in all instances be prevented, by including a seal 46 at theedge of the panels, the likelihood of inadvertent dislodgement of asieve panel can be greatly reduced.

[0075] Yet another embodiment of a mounting pin constructed and arrangedaccording to the principles of the present invention is illustrated inFIG. 13. Mounting pin 50 shown in FIG. 13 is similar to mounting pin 30illustrated in FIG. 11. Mounting pin 50 omits the stem 32 of themounting pin 30 and the lower beveled surface 31B of the head 31 ofmounting pin 30. Preferably, the mounting pin 50 is fabricated fromsteel using a stamping process. Mounting pin 50 has an upperfrustoconical surface 51, which extends downwardly from a cylindricalbody 52 at an angle of approximately 45°. A cylindrical bore or hole 53is formed through the bottom of the cylindrical body 52. The mountingpin 50 is secured to the support structure 1 using well-known plugwelding techniques. As can be seen in FIG. 13, a mounting pin 50 isplaced in a predetermined position and attitude in contact with theupper surface of the vertical member 19 of the support frame 1. A weldmaterial 54 suitable for use with the material from which the mountingpin 50 fabricated is heated to melting and inserted into the hole 53.The molten weld material 54 fuses the mounting pin 50 to the uppersurface of the vertical web 19 of the support frame 1.

[0076] Given the similarity in the profiles of the heads of therespective mounting pins 30 and 50, it is possible to utilize sieveelements 40A and 40B having recesses 41A and 41B as illustrated in FIG.12 with both mounting pins 30 and 50. See FIG. 14. Alternatively, sieveelements having recesses that correspond more closely to the profile ofthe mounting pin 50 may be provided. The sieve elements used inconjunction with mounting pin 50 are secured to and removed from themounting pin 50 in the same manner as described above in connection withmounting pin 30.

[0077] The invention described above may be embodied in other formswithout departing from the spirit or essential characteristics thereof.The embodiments disclosed in this application are to be considered inall respects as illustrative and not restrictive. The scope of theinvention is indicated by the appended claims rather than by theforegoing description and all changes, which come within the meaning andrange of equivalency of the claims, are intended to be embraced therein.

What is claimed is:
 1. A mounting pin for securing a sieve element to asupport frame comprising: a cylindrical body having a bore formedentirely therethrough, the body having a mushroom shaped head with afrustoconical upper surface extending from an upper edge thereof, thebore formed through the body having an outlet at a lower end thereofthat is constructed and arranged such that the upper edge of asupporting rib may be accessed therethrough for the purpose of securingthe mounting pin on the rib, the mounting pin being secured to the upperedge of the rib by forming a weld between the lower end of the body andthe supporting rib through the outlet of the bore.
 2. The mounting pinfor securing a sieve element to a support frame of claim 1 wherein thediameter of the body of the mounting pin is wider than the width of therib on which it is mounted.
 3. A sifting machine comprising: a subframe;a support frame that rests on, and is secured to, the subframe, thesupport frame comprising a plurality of elongate thin ribs having upperedges arranged in a substantially coplanar relationship; each of theribs being further provided with a plurality of mounting pins, eachmounting pin comprising a cylindrical body having a bore formed entirelytherethrough, the body having a mushroom shaped head with afrustoconical upper surface extending from an upper edge thereof, thebore formed through the body having an outlet at a lower end thereofthat is constructed and arranged such that the upper edge of asupporting rib may be accessed therethrough for the purpose of securingthe mounting pin on the rib, the mounting pin being secured to the upperedge of the rib by forming a weld between the lower end of the body andthe supporting rib through the outlet of the bore; and an array of sieveelements arranged in abutting juxtaposition and secured to the supportframe by the mounting pins, the head of each mounting pin engaging apair of adjacent recesses, each recess being formed in the respectiveedges of abutting sieve elements and wherein the pair of adjacentrecesses work together to form a receptacle complementary to the shapeof the head of the mounting pin.
 4. A sieve element for siftingparticulate materials having a plurality of lateral edges comprising abead formed along the lateral edges of the sieve element such that whenthe sieve element is placed in abutting juxtaposition with one or moreadditional sieve elements, the beads on the abutting edges of therespective sieve elements will contact one another to form a sealtherebetween to prevent the flow of particulate materials therebetween.5. A sieve element for sifting particulate materials comprising: a panelhaving a plurality of lateral edges defining a sifting surface of thepanel; a plurality of sieve openings of predetermined size formedthrough the sifting surface of the panel; and, a plurality ofreceptacles formed in the lateral edges of the panel, the receptaclesbeing constructed and arranged to receive therein a mechanism forsecuring the sieve element to a support frame of a sifting machine, thereceptacles being further constructed and arranged such that an area ofthe sifting surface corresponding to the location of a respectivereceptacle has a diameter that is less that twice the diameter of thereceptacle itself.